This project is engineering oriented and investigates treatment technologies for heavily halogenated organic pollutants. These pollutants have generally proven to be resistant to aerobic biochemical treatment measures. Numerous investigators have recognized the potential advantages of reductive dehalogenation as a mechanism for pretreating such compounds for subsequent aerobic transformations. Staged treatments of this nature would eliminate potential hazards from the release of partially dehalogenated products of reductive processes. Both abiotic and biochemically driven reductive dehalogenation of chlorinated solvents are proposed for study and evaluation in this project. The abiotic and biochemical foci will be studied and developed via three model systems that promote dehalogenation of haloorganic compounds that would be applicable for use under field conditions. Proposed work includes: 1) fundamental and applied investigations into the use of semiconductor-macrocycle hybrid catalysts for the reductive dehalogenation of aqueous-phase halogenated organics; 2) parallel development of in situ groundwater treatment systems based on the use of zero-valence metals (Fe and zn) for the reductive dehalogenation of reductive targets; and 3) isolation and identification of the physiological elements responsible for the reductive dehalogenation of carbon tetrachloride by Shewanella putrefaciens 200.